The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
Not Applicable.
1. Field of the Invention
The Weapons Survivability Laboratory (WSL) at China Lake, Calif., routinely participates in the testing and evaluation of onboard aircraft firefighting systems. Obviously, in order to test fire suppression abilities, a fire must be created. As a result, an ignition system is required. However, given the unique needs and short program life of the typical project at WSL, the ignition system would ideally possess various attributes. The invention is more closely associated with igniters typically found in outdoor gas grills and stove burners than other typically used igniters at the WSL.
2. Prior Art
Pyrotechnic Igniters (Squibs)
Squibs are basically nothing more than a small wire coated with a highly flammable substance. In operation, an electrical current is passed through the wire. The wire heats up to the spontaneous combustion temperature associated with the flammable substance. The combustion of the flammable substance then ignites the test item.
For the purpose of most fire suppressant testing, squibs are almost ideal. However, they are not reusable. A test may require a fire ignition point deep within a aircraft or other test object. Thus, the usage of squibs can cause the cost of a test series to increase, because of the time and man hours required to disassemble the test object to the extent that a new squib may be installed.
Elecric Arc (Plasma) Igniters
In an electric arc igniter, a charge is accumulated in a bank of capacitors until said charge reaches some predetermined level. At this point, the charge is dissipated between two electrodes. The air between the electrodes becomes superheated and as a result, the test object is ignited.
Due their ease of use, availibilty and minimal safety considerations, electric arc igniters have been a very popular choice. However, electric arc igniters do possess several drawbacks. The energy delivered is marginal at best, 16-18 joules. They have a fairly high cost per unit, between $3,000.00 and $12,000.00. Due to the large electrical currents involved, they often interfere with test instrumentation. Finally, due to many variables involved, such as fluctuation of power supply and ambient temperature, the precise moment at which the capaciters discharge is largely unpredictable.
Hyperbolic Chemicals
Hypergolic chemicals are chemicals that spontaneously combust upon contact with each other. Within the context of high energy igniters, the most common example would be silene gas. Silene gas spontaneously ignites upon contact with air or oxygen.
When using hypergolic chemicals, safety is the greatest concern. Without exception, the chemicals involved with such systems are hazardous materials and as a result, they require special precautions. Not only are hypergolic chemicals extremely hazardous, they are also corrosive.
The most pertinent prior art is associated with gas igniter systems used in outdoor grills and stove burners. Also, elements of an automobile ignition system are used in the electrical system employed by the invention. However, the particular objects of the invention, the corresponding uses, and overall design of the invention lead to a creation that is novel with respect to that prior art.
The WSL Gas Igniter is, in essence, a small, reuasable oxygen/combustible gas bomb. The device has two main parts. The main parts are the control box and the igniter head.
The control box controls all aspects of operation. It controls the flow of all gases, as well as, the electrically powered ignition system. The igniter head contains an accumulation/combustion chamber in which a combustible mixture of gases is introduced. Also, the combustion chamber contains a small electrical igniter which may be a spark plug. As a result of the reaction produced by the invention, it can not maintain a flame for more than a few milliseconds. In other words, the result is an explosion rather than a sustained flame. In the preferred embodiment of the invention, the gases utilized are oxygen and acetylene. However, any combustible gas with a low molecular weight may be used, in place of acetylene, such as hydrogen.
The invention uses oxygen, rather than air, because the integrity of a test area must be maintained. Any contamination of the test area can affect the results of the test. The explosion created by the invention is isolated from the outside environment, so that, the data collected is reliable. Creating an environment free from outside influences, such as air, enables the data to accurately reflect the fire suppression capability of a particular area of a test article.
A method of testing fire suppression capability is disclosed herein. The first step is placing a gas igniter, as described herein, in a desired position within a test article. The second step is initiating a control signal that simultaneously energizes a spark system and opens the gas control valves. The next step is introducing a combustible mixture into the combustion chamber, then removing the control signal. The control signal closes gas control valves and fires the spark system. The next step is igniting the combustible mixture causing the combustible mixture to produces an explosion that ignites the test article, then testing the fire suppression capability of the test article.
The Weapons Survivability Laboratory (WSL) at China Lake, Calif., routinely participates in the testing and evaluation of onboard aircraft firefighting systems. Obviously, in order to test fire suppression abilities, a fire must be created. As a result, an ignition system is required. However, given the unique needs and short program life of the typical project at WSL, the ignition system would ideally possess various attributes.
It is an object of the invention to deliver high energy levels, greater than 20 joules, to ensure reliable ignition of high flashpoint materials.
It is another object of the invention to allow the ignition to be precisely timed to permit the construction of an accurate test timeline.
It is a further object of the invention to prevent interference with any instrumentation that might also be involved with the test to ensure that the confidence level of all data is acceptable.
It is a further object of the invention to create a test environment free from outside factors that may affect the results.
It is a further object of the invention to be reusable as tests may require a point of ignition deep within an aircraft that makes igniter replacement a very labor intensive process.
It is a further object of the invention to be reasonably inexpensive as there is a finite chance that the igniter will be destroyed on any given test.
It is a further object of the invention to be readily adaptable to almost any test article or situation.
It is a further object of the invention to present acceptable safety risks.
It is a further object of the invention to facilitate a reaction between gases that produces an explosion which ignites the test article.
The present invention provides a device that satisfies all the desired objectives.